Prior art damper controls for attic vent pipes are complex requiring complex parts and lever arrangements. This in part has been required since the amount of linear movement obtained from a thermostatic bellows or bimetal spring control is small as compared with the amount of movement of a flap damper valve in a 12" diameter pipe for example. It is well known that the simpler a device is the greater the reliability since a greater number of interrelated moving parts produce more places at which operation can fail.